Reactor vessel handling method

ABSTRACT

One of methods for carrying out a reactor vessel according to the present invention comprises the steps of removing an overhead traveling crane in a reactor containment vessel of a pressurized water reactor, or the steps of, in an area where an overhead traveling crane is installed, operating the overhead traveling crane to move aside for creating a space, through which the reactor vessel is able to pass, and then carrying out the reactor vessel through an opening provided in a top portion of the reactor containment vessel. With the present method, the reactor vessel of the pressurized water reactor can be carried out in a short time with high efficiency.

TECHNICAL FIELD

[0001] The present invention relates to methods for carrying in and outa reactor vessel, which are employed in a pressurized water reactor(hereinafter abbreviated to a “PWR”) for work of, e.g., carrying out areactor vessel when the reactor vessel is to be replaced ordecommissioned.

BACKGROUND ART

[0002] A reactor vessel is the most important equipment in a nuclearpower plant. The service period of a nuclear power plant generallydepends on the lifetimes of a reactor vessel and various units ofauxiliary equipment installed inside and outside the reactor vessel.Also, when the service period of a nuclear power plant is expired, thenuclear power plant must be dismantled and decommissioned. In such anenvironment, it is important to prolong the service period of anexisting old nuclear power plant that has been operated for relativelylong years and is still now in commission.

[0003] In an existing old nuclear power plant, the plant has beenrefreshed or rejigged by repair and replacement of equipment other thana reactor vessel and core internals. For further prolongation of theservice period, however, there has arisen the necessity of repairing andreplacing the reactor vessel and the core internals as well.

[0004] In fact, replacement of core internals is already implemented ina boiling water reactor (BWR). Also, replacement of a reactor-vesselupper lid is already implemented in a PWR. From that background,establishing techniques for replacement of a reactor vessel includingcore internals has been required as one measure of preventivemaintenance for an existing old nuclear power plant. In thosetechniques, it is important to make a plant downtime as short aspossible.

[0005] As first prior art, methods for carrying out a reactor vessel aredisclosed in Japanese Unexamined Patent Application Publication Nos.8-62368 and 9-145882. However, those prior-art methods are concernedwith carrying-out of a reactor pressure vessel of a BWR, and cannot bedirectly applied to carrying-out of a pressure vessel of a PWR.

[0006] Japanese Unexamined Patent Application Publication No. 11-84052discloses, as second prior art, a method for carrying out core internalsof a PWR through a space left around a girder for a polar crane(overhead traveling crane). This prior art can be applied tocarrying-out of core internals, but not to carrying-out of a reactorvessel. The reasons why the above prior art cannot be applied tocarrying-out of a reactor vessel reside in three points as follows:

[0007] (1) The reactor vessel cannot pass through the space left aroundthe girder for the polar crane.

[0008] (2) The polar crane installed in a reactor containment vessel(hereinafter referred to as a “containment vessel”) has not a capacitycapable of lifting the reactor vessel and an associated radiation shieldtogether.

[0009] (3) The reactor vessel including the radiation shield combinedtherewith cannot be carried out through an equipment carrying-in openingprovided in the containment vessel.

[0010] Disclosure of Invention

[0011] An object of the present invention is to provide a reactor vesselhandling method, which is able to carry in and out a reactor vessel of apressurized water reactor in a short time with high efficiency.

[0012] According to one aspect of the present invention, an overheadtraveling crane in a reactor containment vessel of a pressurized waterreactor is removed, and then a reactor vessel is carried out through anopening provided in a top portion of the reactor containment vessel.

[0013] According to another aspect of the present invention, in an areawithin a reactor containment vessel of a pressurized water reactor wherean overhead traveling crane is installed, the overhead traveling craneis operated to move aside for creating a space, through which a reactorvessel is able to pass, and then the reactor vessel is carried outthrough an opening provided in a top portion of the reactor containmentvessel.

[0014] According to still another aspect of the present invention, anoverhead traveling crane in a reactor containment vessel of apressurized water reactor is reinforced, a reactor vessel is lifted upto an operating floor by using the reinforced overhead traveling crane,and then the reactor vessel is carried out through an opening providedin a side wall of the reactor containment vessel.

[0015] According to still another aspect of the present invention, in astate in which an overhead traveling crane in a reactor containmentvessel of a pressurized water reactor is removed, a new reactor vesselis carried in to a predetermined position within the reactor containmentvessel through an opening provided in a top portion of the reactorcontainment vessel.

[0016] According to still another aspect of the present invention, in astate in which an overhead traveling crane in a reactor containmentvessel of a pressurized water reactor is reinforced, a new reactorvessel is carried in to a predetermined position within the reactorcontainment vessel through an opening provided in a side wall of thereactor containment vessel.

[0017] In a reactor containment vessel, to which any of theabove-described methods of the present invention is applied, an openingallowing the reactor vessel to be carried out through the opening isprovided in at least one of a top wall and a side wall of the reactorcontainment vessel.

[0018] The present invention set forth above can be applied tocarrying-out and -in of a reactor vessel of a PWR when the reactorvessel is to be replaced. The present invention can also be applied tocarrying-out of a reactor vessel of a PWR when the reactor vessel is tobe decommissioned.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1A is a flowchart showing a method for replacing a reactorvessel according to a first embodiment of the present invention.

[0020]FIG. 1B is a flowchart showing a method for replacing a reactorvessel according to a first embodiment of the present invention.

[0021]FIG. 2 is a schematic vertical sectional view of a reactorshielding building in a PWR plant to which the present invention isapplied.

[0022]FIG. 3 is a perspective view, partly broken away, of a reactorvessel shown in FIG. 2.

[0023]FIG. 4 is a schematic vertical sectional view of a reactor vesseland surroundings thereof during work for making a reactor open.

[0024]FIG. 5 is a schematic vertical sectional view of the reactorvessel and surroundings thereof during work for removing upper coreinternals 20.

[0025]FIG. 6 is a schematic vertical sectional view of the reactorvessel and surroundings thereof during work for taking out a fuelassembly.

[0026]FIG. 7 is a schematic vertical sectional view of the reactorvessel and surroundings thereof, showing a state after cutting pipesconnected to an inlet nozzle and an outlet nozzle.

[0027]FIG. 8 is a schematic vertical sectional view of the reactorshielding building after setting up a heavy-duty crane and forming atemporary opening.

[0028]FIG. 9 is a schematic vertical sectional view of the reactorvessel and surroundings thereof after temporarily placing a shield in areactor cavity.

[0029]FIG. 10 is a schematic vertical sectional view of the reactorvessel and surroundings thereof, showing a state in which the reactorvessel and the shield are united into one.

[0030]FIG. 11 is a schematic vertical sectional view of a containmentvessel, showing a state immediately before carrying out a large-sizeblock, which comprises the reactor vessel and the shield having beenunited into one, through the temporary opening.

[0031]FIG. 12A is a view showing a state before attaching a bottomshield.

[0032]FIG. 12B is a view showing a state after attaching the bottomshield.

[0033]FIG. 13 is a view showing a state in which the large-size block iscarried out through the temporary opening of the reactor shieldingbuilding.

[0034]FIG. 14 is a view showing a state immediately before carrying thelarge-size block into a storage container.

[0035]FIG. 15A is a view showing a state in which the large-size blockis tilted down to be laid on a trailer.

[0036]FIG. 15B is a view showing one example of a tilting-down apparatusprovided on the trailer for tilting down the large-size block.

[0037]FIG. 16A is a side view, partly broken away, showing details of anattachment unit for a shield as another example.

[0038]FIG. 16B is a top plan view of FIG. 16A.

[0039]FIG. 17A is a flowchart showing a method for replacing a reactorvessel according to a second embodiment of the present invention.

[0040]FIG. 17B is a flowchart showing a method for replacing a reactorvessel according to a second embodiment of the present invention.

[0041]FIG. 18 is a view showing a state in which a temporary opening isformed in a side wall of a containment vessel.

[0042]FIG. 19 is a view showing a state in which a polar crane isreinforced.

[0043]FIG. 20 is a view showing a state in which the large-size block istilted down in the containment vessel to be laid on a flatcar.

BEST MODE FOR CARRYING OUT THE INVENTION

[0044] (First Embodiment)

[0045] A description is made of a first embodiment in which the presentinvention is applied to replacement of a reactor vessel in a pressurizedwater reactor plant (hereinafter abbreviated to a “PWR plant”). In thisembodiment, after removing a polar crane within a reactor containmentvessel (simply called a containment vessel), a reactor vessel(hereinafter abbreviated to “RV”) and core internals are carried outtogether and replaced with a new set of reactor vessel and coreinternals.

[0046]FIG. 2 is a schematic vertical sectional view of a reactorshielding building in the PWR plant to which the present invention isapplied. As shown in FIG. 2, a reactor shielding building 1 is of areinforced concrete structure, and a steel-made containment vessel(hereinafter abbreviated to “CV”) 3 is installed inside the reactorshielding building 1. Walls and floors of a reinforced concretestructure or a steel-framed concrete structure are provided in a lowerportion of the CV 3 to define a reactor cavity 5, and the RV 2 isinstalled at the center of a bottom portion of the reactor cavity 5.

[0047] An operation floor 7, on which various kinds of works in the CV 3are performed, is formed in an upper portion of the reactor cavity 5. Anequipment carrying-in opening 4 is provided on the upper side of theoperation floor 7 so that various types of equipment may be carried outto the exterior of the reactor shielding building 1 through the opening4. A steam generator (hereinafter abbreviated to “SG”) 8 is arranged ina space surrounded by a shied wall 6. An annular rail 10 is installedjust below a dome-shaped ceiling of the CV 3, and a polar crane 9 ismounted on the annular rail 10. The polar crane 9 is an overheadtraveling crane comprising a girder 9 a and a trolley 9 b, and it isused-to move large-weight components in the CV 3.

[0048]FIG. 3 is a perspective view, partly broken away, of the RV 2shown in FIG. 2. As shown in FIG. 3, an upper lid 2 a is fixed to a bodyof the RV 2 through a flange 2 b using bolts 2 c. The RV 2 has a heightof about 10 m and a diameter of about 4 m. Core internals 50, describedlater, are installed inside the RV 2. A core tank 12 is arranged at thecenter of the RV 2, and a fuel assembly 13 is arranged inside the coretank 12. The core tank 12 is a cylindrical core internal arranged in theRV 2 so as to surround a rector core.

[0049] An upper core support plate 17 is detachably provided at an upperend of the core tank 12 and is attached to an upper core plate 16 by aplurality of upper core support posts 19. The upper core plate 16, theupper core support plate 17, a control rod cluster 18, and the uppercore support posts 19 constitute upper core internals 20. A lower coresupport plate 14 and a lower core plate 15 are provided in a lowerportion of the core tank 12. The core tank 12, the lower core supportplate 14, and the lower core plate 15 constitute lower core internals21.

[0050] The core internals 50 comprise the upper core internals 20 andthe lower core internals 21. The core internals 20 and 21 can beseparately taken out to the exterior of the RV 2. An inlet nozzle 22 andan outlet nozzle 23 both provided in the RV 2 are connected via pipes tothe SG 8 installed in the CV 3.

[0051]FIG. 1A and FIG. 1B are flowchart showing a method for replacingthe RV according to the first embodiment. First, work for making thereactor open is performed in step S1. In the reactor opening work, theupper lid 2 a of the RV 2 is removed. FIG. 4 is a schematic verticalsectional view of the RV 2 and surroundings thereof during the reactoropening work. Numeral 18 a denotes a control rod driving mechanism.

[0052] Then, in step S2, the upper core internals 20 are removed. Thiswork is performed in a state in which a core water level is raised tofully fill the reactor cavity 5 with water. FIG. 5 is a schematicvertical sectional view of the RV 2 and surroundings thereof during thework for removing the upper core internals 20. The upper core plate 16,the upper core support plate 17, the control rod cluster 18, and theupper core support posts 19, which constitute the upper core internals20, are removed together.

[0053] Then, in step S3, all fuel is taken out and moved to a fuel pool.This work is performed while the core water level is kept raised tofully fill the reactor cavity 5 with water.

[0054]FIG. 6 is a schematic vertical sectional view of the RV 2 andsurroundings thereof during the work for taking out a fuel assembly 13with a fuel replacing apparatus 13 a.

[0055] Then, in step S4, the upper core internals 20 are returned intothe RV 2 and mounted in place. When the upper core internals 20 are notreplaced, this step can be omitted.

[0056] Then, in step S5, the interior of the RV 2 is decontaminated toeliminate radioactive materials deposited on an inner wall of the RV 2and the core internals 50. Chemical decontamination using chemicals isone example of decontaminating methods. Performing the decontaminationmakes it possible to simplify a shield that is used when carrying outthe RV 2 to the exterior of the reactor shielding building 1. When thedecontamination is not performed, this step can be omitted.

[0057] Then, in step S6, pipes 24 and 25 connected to the inlet nozzle22 and the outlet nozzle 23 respectively are cut off. On that occasion,for reducing an exposure rate of workers engaged in the pipe cuttingwork, water sealing plugs 22 a and 23 a are attached to the inlet nozzle22 and the outlet nozzle 23 respectively from the inside of the reactorwhile the reactor cavity 5 is kept fully filled with water.Subsequently, the reactor water level is lowered to a position of theflange 2 b in the upper portion of the RV 2. Thereafter, for shuttingoff radiations from the inner side of the reactor, a shield lid 26having a radiation shielding capability is attached to the flange 2 b bybolts 26 a. Then, after securing a space for the pipe cutting work,structural members, such as sealing materials, located above the nozzlesand thermal insulating materials located around the nozzles are removed.With removal of those materials, the RV 2 is prevented from interferingwith the nozzles when it is carried out.

[0058]FIG. 7 is a schematic vertical sectional view of the RV 2 andsurroundings thereof, showing a state after cutting off the pipes 24 and25 connected respectively to the inlet nozzle 22 and the outlet nozzle23. To prevent radioactive materials in the reactor from flowing out tothe exterior of the RV 2, closure plates 22 b and 23 b are attached tothe respective nozzles after the pipe cutting work from the outer sideof the RV 2.

[0059] Then, in step S7, a radiation shielding material, such as mortar,is filled in the reactor. The shielding material is filled through ahose or the like inserted in a hole, which is formed in the shield lid26 beforehand, Filling the shielding material into a reactor bottomportion makes it possible to omit a bottom plate of a radiation shield28, described later, for the RV 2. After filling the shielding material,the hole formed in the shield lid 26 is plugged. When the radiation dosefrom the reactor bottom portion is not more than a transport standardvalue, this step may be omitted.

[0060] Then, in step S8, cables 37 connected to the bottom portion ofthe RV 2 for in-core instrumentation are removed. In step S9, aheavy-duty crane 30 for carrying out (in) the RV 2 is set up outside thereactor shielding building 1. Then, in step S10, a temporary opening 31,through which the RV 2 can be carried out (in), is formed in the ceiling(top wall) of the reactor shielding building 1 and the containmentvessel 3. A shutter 32 capable of opening and closing is provided abovethe temporary opening 31 for protection against rain. FIG. 8 is aschematic vertical sectional view of the reactor shielding building 1after setting up the heavy-duty crane 30 and forming the temporaryopening 31.

[0061] Then, in step S11, the polar crane 9 is removed and, in step S12,the radiation shield 28 is carried in. When carrying in the radiationshield 28, reinforcing members 27 are first placed at the bottom of thereactor cavity 5 so as to surround the RV 2. The reinforcing members 27serve to distribute the weight of the radiation shield 28 over thebottom of the reactor cavity 5. Subsequently, the shutter 32 is opened,and the radiation shield 28 is carried into the CV 3 through thetemporary opening 31 and temporarily placed on the reinforcing members27 by using the heavy-duty crane 30. To that end, the temporary opening31 is set to a size allowing the radiation shield 28 to be carried in(out) through it. The radiation shield 28 has a cylindrical shape and isprovided at its upper end with a shield upper lid 28 a in the form of adisk. The radiation shield 28 serves to shut off radiations from the RV2. FIG. 9 is a schematic vertical sectional view of the RV 2 andsurroundings thereof, showing a state in which the radiation shield 28is temporarily placed in the reactor cavity 5 and a sling 30 a isattached to the shield lid 26.

[0062] Then, in step S13, the RV 2 is lifted up and united with theradiation shield 28. The strongback (sling) 30 a as a jig for lifting upthe RV 2 is attached to the shield lid 26 using eight to ten pieces ofbolts 26 a. The sling 30 a is suspended by the heavy-duty crane 30. Theshield upper lid 28 a has a slit-like opening through which the sling 30a is able to pass, and has hooks 28 b provided on its upper side forhanging the radiation shield 28. By raising the sling 30 a with theheavy-duty crane 30, the RV 2 is lifted up. The RV 2 is combined withthe radiation shield 28 just by lifting up the RV 2 such that the shieldlid 26 is brought into abutment with the shield upper lid 28 a.

[0063] Subsequently, the opening of the shield upper lid 28 a is coveredwith a protective sheet 28 c, and ends of the protective sheet 28 c arefixedly attached in a sealed-off manner using a sealing tape. Likewise,a lower end of the radiation shield 28 is covered with a protectivesheet 28 d whose ends are also fixedly attached in a sealed-off mannerusing a sealing tape. Each of the protective sheets 28 c and 28 d can beformed of, e.g., a polyvinyl chloride sheet. FIG. 10 is a schematicvertical sectional view of the RV 2 and surroundings thereof, showing astate in which the RV 2 is lifted up and united with the radiationshield 28.

[0064] Thus, the radiation shield 28 can be easily combined with the RV2 in a surrounding relation in a short time just by lifting up the coreinternals 50 together (in union) with the RV 2. Also, since the openingsof the radiation shield 28 are sealed off with the protective sheets 28c and 28 d, radioactive dust deposited on the surface of the RV 2 can beprevented from scattering to the exterior.

[0065] Next, in the state of the radiation shield 28 being combined withthe RV 2, the surfaces of the shield and the protective sheets aredecontaminated. The fact that the surface dose rate has been lowered tosuch a level as not affecting an external environment of the containmentvessel is confirmed by a contamination test. FIG. 11 is a schematicvertical sectional view of the CV 3, showing a state immediately beforelifting up a large-size block 51, which includes the radiation shield 28and the RV 2 united into one, by the heavy-duty crane 30 and carryingout the large-size block 51 through the temporary opening 31.

[0066] As shown in FIG. 11, the radiation shield 28 covers the whole ofthe RV 2 from the top to the bottom thereof. Since the bottom portion ofthe RV 2 generates a lower radiation dose than a core portion locatedabove the bottom portion of the RV 2 and is filled with the radiationshielding material, it is not required to attach a radiation shield tothe bottom portion of the RV 2 in most cases.

[0067] When it is required to attach such a shield to the bottom portionof the RV 2, the shield is attached to the reactor bottom portion instep S13. A method for attaching the shield is now described withreference to FIGS. 12A and 12B. FIG. 12A shows a state before attachinga bottom shield 29, and FIG. 12B shows a state after attaching thebottom shield 29.

[0068] As shown in FIG. 12A, the large-size block 51 is lifted up by theheavy-duty crane 30 to a level above the operation floor 7, rails 29 aare set at the top of the reactor cavity 5, and a flatcar 29 b includingthe bottom shield 29 laid thereon is rested on the rails 29 a. Then, asshown in FIG. 12B, the flatcar 29 b including the bottom shield 29 laidthereon is moved to a position right below the large-size block 51, andthe large-size block 51 is descended to a height at which it contactsthe bottom shield 29. Thereafter, the large-size block 51 and the bottomshield 29 are joined to each other by, e.g., bolts.

[0069] In such a way, when carrying the RV 2 out of the reactorshielding building 1, the surface dose rate of the radiation shield 28can be reduced to a level lower than a reference value (limit value).

[0070] Then, in step S14, the RV 2 is carried out. More specifically,the RV 2 is lifted up as the large-size block 51 in union with theradiation shield 28 and the core internals 50. The large-size block 51is carried out to the exterior through the temporary opening 31 of thereactor shielding building 1. After carrying out the large-size block 51to the exterior of the reactor shielding building 1, the shutter 32 isclosed. FIG. 13 is a view showing a state in which the large-size block51 is carried out by the heavy-duty crane 30 through the temporaryopening 31 of the reactor shielding building 1.

[0071] Then, in step S15, the large-size block 51 carried out of thereactor shielding building 1 is carried into a storage container 40. Onthat occasion, a fore end 30 b of the heavy-duty crane 30 is moved froma position right above the temporary opening 31 of the reactor shieldingbuilding 1 to a position right above the storage container 40 whilekeeping the large-size block 51 hanged by the heavy-duty crane 30.Thereafter, the large-size block 51 is descended and carried into thestorage container 40.

[0072]FIG. 14 is a view showing a state immediately before carrying thelarge-size block 51 into the storage container 40 in step S15. Thestorage container 40 is provided under the ground near the reactorshielding building 1, and has a structure capable of containing thelarge-size block 51 in an upright posture. Thus, the large-size block 51can be carried into the storage container 40 by using the heavy-dutycrane 30 while the large-size block 51 is kept in the same state as thatjust after being carried out of the reactor shielding building 1. Aftercarrying the large-size block 51 into the storage container 40, a lid isattached to the storage container 40 for bringing it into a sealed-offcondition.

[0073] As an alternative, in step S15, the large-size block may beloaded on a trailer, transported to the storage container, and thencarried into it. This method is effective when the storage container isremote from the reactor shielding building. Also, the storage containermay be provided in a building of a ridge continuation with the reactorshielding building. The storage container may be provided on the groundto be able to contain the large-size block in a horizontally laid state.

[0074] A method for loading the large-size block on a trailer (flatcar)in a horizontally laid state is now described. The large-size block 51hanged by the heavy-duty crane 30 is moved to a tilting-down apparatusprovided on a trailer 34, which is stopped near the reactor shieldingbuilding 1. Then, the large-size block 51 is horizontally laid by thetilting-down apparatus to be loaded on the trailer 34.

[0075]FIG. 15A is a view showing a state in which the large-size block51 is tilted down to be laid on the trailer 34, and FIG. 15B is a viewshowing one example of the tilting-down apparatus provided on thetrailer for tilting down the large-size block. In such a case, atilting-down shaft 28 g is attached to the radiation shield 28beforehand.

[0076] The large-size block 51 is slowly descended toward a tilting-downbearing 35 while being vertically hanged by heavy-duty crane wires 30 c,and at the same the trailer 34 is slowly moved in a directioncorresponding to the direction in which the large-size block 51 is to betilted down. As a result, the radiation shield 28 is rotated about thetilting-down shaft 28 g, and the large-size block 51 is gradually tilteddown from the vertically hanged state. On that occasion, the distanceand speed by and at which the trailer 34 is moved and the distance andspeed by and at which the large-size block 51 is descended, are adjustedin a proper combination so that the weight imposed on the tilting-downshaft 28 g is reduced to, e.g., about a half the total weight of thelarge-size block.

[0077] In such a way, the large-size block 51 is gradually horizontallylaid on a platform 36 of the trailer 34 while avoiding excessive loadsfrom being imposed on the tilting-down shaft 28 g and the tilting-downbearing 35. After horizontally laying the large-size block 51 on theplatform 36 of the trailer 34, the large-size block 51 is fixed in placeby, e.g., wires. The work for tilting down the large-size block is thuscompleted.

[0078] Through the procedures described above, the work for carryingout, as the large-size block 51, the RV 2 in union with the radiationshield 28 and the core internals 50 is completed.

[0079] Then, in step S16, a new reactor vessel (new RV) 2 is lifted upby the heavy-duty crane 30 and is carried in to a predetermined positionwithin the containment vessel 3 (i.e., the bottom portion of the reactorcavity 5) through the temporary opening 31. At this time, the new RV 2is carried in together with the lower core internals 21 mounted in thenew RV 2. Alternatively, the new RV 2 and the lower core internals 21may be carried in separately.

[0080] Then, in step S17, the removed polar crane 9 is carried into thecontainment vessel 3 through the temporary opening 31 for restoration tothe same state as that before removal. Subsequently, the temporaryopening 31 is closed in step S18, and the heavy-duty crane 30 isdismantled in step S19. Further, in step S20, an outlet pipe and aninlet pipe to be connected to the new RV 2 are connected respectively tothe outlet nozzle and the inlet nozzle for restoration to the same stateas that before replacement. In step S21, the cables are attached to abottom portion of the new RV 2 for restoration to the same state as thatbefore replacement.

[0081] Then, fuel is charged in step S22 and the upper core internals 20are mounted in step S23 for restoration to the same state as that beforeremoval. Thereafter, in step S24, the operation of the reactor isstarted. A series of work steps for replacing the reactor vessel iscompleted through the procedures described above.

[0082] Another example of the radiation shield 28 to be combined withthe RV 2 will be described below with reference to FIGS. 16A and 16B. Aradiation shield 28 of this example differs from that shown in FIG. 9 inhaving, instead of the shield upper lid 28 a, stopper beams 28 e thatare brought into abutment with the upper lid of the RV 2. The remainingstructure is the same as that shown in FIG. 9, and hence a descriptionthereof is omitted here.

[0083]FIG. 16A and FIG. 16B show a state in which the RV 2 is lifted upand combined with the radiation shield 28 of this example. Specifically,FIG. 16A is a side view, partly broken away, showing details of anattachment unit for the radiation shield 28, and FIG. 16B is a top planview of FIG. 16A. As shown in FIG. 16B, opposite ends of each of fourstopper beams 28 e are fixed to an upper surface of the radiation shield28 by set bolts 28 f. The stopper beams 28 e are arranged at positionsalmost evenly spaced from each other in the circumferential directionsuch that the stopper beams will not interfere with the sling 30 a. Ahook 28 h for hanging the radiation shield 28 is provided at the centerof each stopper beam 28 e.

[0084] In the radiation shield 28 of this example, since centralportions of the stopper beams 28 e are brought into abutment with theshield lid 26, the radiation shield 28 can be easily combined with theRV 2 just by lifting up the RV 2. Depending on cases, the height of theradiation shield 28 can be reduced to a height enough to cover nearly alevel of-the outlet nozzle (or the inlet nozzle) by filling a shieldingmaterial in the RV 2. In such a case, the height of the radiation shield28 may be reduced to such an extent that the stopper beams 28 e arebrought into abutment with the outlet nozzle (or the inlet nozzle). Inthat case, the radiation shield 28 can also be easily combined with theRV 2 in a short time just by lifting up the RV 2.

[0085] With the embodiment described above, the reactor vessel can becarried out and in with high efficiency in a short time in a state wherethe polar crane is removed. It is therefore possible to shorten the termof work for replacing the reactor vessel and hence to shorten thedowntime of the nuclear power plant.

[0086] Further, when carrying out the reactor vessel, the surface doserate of the shield for the reactor vessel can be reduced to a levellower than the limit value. Moreover, since workers are less required toaccess the reactor vessel when the shield is combined with the reactorvessel, the radiation exposure rate of the workers can be reduced duringthe work for carrying out the reactor vessel.

[0087] Additionally, in the embodiment described above, work fordraining reactor water in the RV 2 after the end of step S6 may beomitted. In that case, the remaining reactor water is effective to shutoff radiations from the core internals 50. It is therefore possible tofurther reduce the surface dose rate of the RV 2, and hence to omit thestep S7 of filling mortar (shielding material). Also, instead of mortar,powder (or fine particles) of, e.g., lead or steel may be sealed off inthe reactor.

[0088] While, in the embodiment described above, the polar crane isremoved in step S11, this step is not limited to removal of the polarcrane. For example, the polar crane may be operated to move aside forcreating a space, through which the reactor vessel and the shield areable to pass, in an area within the reactor containment vessel where thepolar crane is installed. In that case, the polar crane is restored tothe original state in step S17.

[0089] (Embodiment 2)

[0090] Next, a description is made of a second embodiment in which thepresent invention is applied to replacement of a reactor vessel in a PWRplant. In this embodiment, after reinforcing a polar crane, a large-sizeblock including a reactor vessel (RV) is lifted up by the reinforcedpolar crane and then carried out through an opening formed so as topenetrate side walls of a containment vessel (CV) and a reactorshielding building for replacement with a new reactor vessel.

[0091]FIG. 17A and FIG. 17B are flowchart showing a method for replacingthe RV according to the second embodiment. Steps T1-T8 and T21-T25 inFIGS. 17A and 17B are the same as steps S1-S8 and S20-S24 in FIGS. 1Aand 1B. This second embodiment differs from the first embodiment insteps T9-T20 in FIGS. 17A and 17B. Other procedures are the same asthose in the first embodiment and a description thereof is omitted here.Steps T9-T20 in this embodiment will be described below.

[0092] In step T9, a temporary opening 4 a is formed so as to penetrateside walls of a CV 3 and a reactor shielding building having 1, thetemporary opening 4 a having a size allowing a large-size block 51including an RV 2 to be carried out through it in a horizontally laidstate. FIG. 18 shows a state in which the temporary opening 4 a enablingthe large-size block 51 (not shown in FIG. 18) to be carried outtherethrough is formed in the side wall of the CV 3 at a level above anoperating floor 7.

[0093] Although an equipment carrying-in opening 4 is provided in the CV3 for carrying out/in large-size equipment through it, the size of theequipment carrying-in opening 4 is not enough to carry out thelarge-size block 51 including a radiation shield 28 and the RV 2, asdescribed above. Therefore, the temporary opening 4 a is newly formed soas to penetrate both the CV 3 and the reactor building 1. A shutter 4 bcapable of opening and closing is provided to close the temporaryopening 4 a. The temporary opening 4 a may be formed at a differentposition from the equipment carrying-in opening 4, but the termnecessary for the work can be cut down by enlarging the existingequipment carrying-in opening 4 to such an extent that the temporaryopening 4 a is formed.

[0094] Then, in step T10, a polar crane 9 is reinforced. The existingpolar crane has a capacity of about 100 tons. On the other hand, theweight of the large-size block 51 including core internals 50, the RV 2and the radiation shield 28 amounts to 400 to 500 tons. For that reason,the polar crane 9 is reinforced to be capable of lifting up thelarge-size block 51 having such a large weight. FIG. 19 shows a state inwhich the polar crane 9 is reinforced by erecting reinforcing members 33on the operating floor 7 in the CV 3. The reinforcing members 33 may beprovided with pulleys or the likes so that the reinforcing members areable to freely move on the operating floor 7 in conjunction with thepolar crane 9.

[0095] Then, in step T11, an auxiliary trolley 9 c with a reinforcedlifting apparatus is mounted. More specifically, the auxiliary trolley 9c comprising a chain jack (or a hydraulic jack, etc.), which has acapacity capable of lifting up the large-size block with the weight of400 to 500 tons, is mounted on a girder 9 a.

[0096] Then, in step T12, the radiation shield 28 is carried in throughthe temporary opening 4 a. As with step S12 in the first embodiment, theradiation shield 28 is temporarily placed on the RV 2 (or reinforcingmembers 27) in a bottom portion of a reactor cavity 5. The radiationshield 28 is provided with a tilting down shaft 28 g, which is similarto that shown in FIGS. 15A and 15B, for tilting down the RV 2.

[0097] Then, in step T13, the RV 2 and the radiation shield 28 arecombined with each other. The RV 2 is lifted up by the reinforced polarcrane 9. As with step S13 in the first embodiment, the RV 2 and theradiation shield 28 can be easily united into one in a short time byjust lifting up the RV 2 to such an extent that a shield lid 26 of theRV 2 is brought into abutment with a shield upper lid 28 a.

[0098] Then, in step T14, a flatcar (trailer) 34 a provided with atilting-down bearing 35 is carried into the CV 3 and set up on theoperating floor 7 for tilting down the RV 2.

[0099] Then, in step T15, the large-size block 51 including the RV 2combined with the radiation shield 28 is tilted down. The tilting-downof the large-size block 51 is performed in a similar manner as describedabove in connection with FIGS. 15A and 15B. FIG. 20 is a view showing astate in which the large-size block 51 is tilted down in the CV 3 to belaid on the flatcar 34 a.

[0100] Then, in step T16, the large-size block 51 in a state of beinghorizontally laid on the flatcar 34 a is carried out of the reactorshielding building 1 through the temporary opening 4 a. In step T17,while keeping the large-size block 51 horizontally laid on the flatcar34 a, the large-size block 51 is transported to a storage container 40for the RV 2, which is installed in, e.g., the nuclear power plant site,and then carried into the storage container 40.

[0101] Then, in step T18, a new reactor vessel (new RV) 2 is carriedinto the CV 3 through the temporary opening 4 a by using the flatcar 34a. After carrying the new RV 2 into the CV 3, the new RV 2 is tilted upby the reinforced polar crane 9 in accordance with the procedurereversal tot that in step T15. Further, the new RV 2 is lifted up by thereinforced polar crane 9 and is installed in the reactor cavity 5.

[0102] Then, the reinforcing members 33 and the auxiliary trolley 9 cfor the polar crane 9 are removed in step T19, and the temporary opening4 a is closed in step T20. Subsequent steps T21 to T25 are performed inthe same manners as in steps S20 to S24 shown in FIGS. 1A and 1B. Thework for carrying out the large-size block 51, which includes the coreinternals 50, the RV 2 and the radiation shield 28 united into one, andthe work for carrying the new RV 2 are thereby completed.

[0103] With this embodiment, carrying-out and -in of the reactor vesselcan be implemented in a short time with high efficiency by using thereinforced polar crane. It is therefore possible to shorten the term ofwork for replacing the reactor vessel and hence to shorten the downtimeof the nuclear power plant. Further, as with the first embodiment, whencarrying out the reactor vessel, the surface dose rate of the shield forthe reactor vessel can be reduced to a level lower than the limit value,and the radiation exposure rate of workers can be reduced.

1. A reactor vessel handling method comprising the steps of removing anoverhead traveling crane in a reactor containment vessel of apressurized water reactor, and then carrying out a reactor vesselthrough an opening provided in a top portion of said reactor containmentvessel.
 2. A reactor vessel handling method comprising the steps of, inan area within a reactor containment vessel of a pressurized waterreactor where an overhead traveling crane is installed, operating saidoverhead traveling crane to move aside for creating a space, throughwhich a reactor vessel is able to pass; and then carrying out saidreactor vessel through an opening provided in a top portion of saidreactor containment vessel.
 3. A reactor vessel handling methodcomprising the steps of reinforcing an overhead traveling crane in areactor containment vessel of a pressurized water reactor, lifting areactor vessel up to an operating floor by using the reinforced overheadtraveling crane, and then carrying out said reactor vessel through anopening provided in a side wall of said reactor containment vessel.
 4. Areactor vessel handling method according to claim 3, wherein anequipment carrying-in opening in said reactor containment vessel isutilized as said opening.
 5. A reactor vessel handling method comprisingthe steps of removing an overhead traveling crane in a reactorcontainment vessel of a pressurized water reactor, and carrying out areactor vessel through an opening provided in a top portion of saidreactor containment vessel; and then carrying in a new reactor vessel toa predetermined position within said reactor containment vessel throughsaid opening.
 6. A reactor vessel handling method comprising the stepsof, in an area within a reactor containment vessel of a pressurizedwater reactor where an overhead traveling crane is installed, operatingsaid overhead traveling crane to move aside for creating a space,through which a reactor vessel is able to pass, and carrying out saidreactor vessel through an opening provided in a top portion of saidreactor containment vessel; and then carrying in a new reactor vessel toa predetermined position within said reactor containment vessel throughsaid opening.
 7. A reactor vessel handling method comprising the stepsof reinforcing an overhead traveling crane in a reactor containmentvessel of a pressurized water reactor, lifting a reactor vessel up to anoperating floor by using the reinforced overhead traveling crane, andcarrying out said reactor vessel through an opening provided in a sidewall of said reactor containment vessel; and then carrying in a newreactor vessel to a predetermined position within said reactorcontainment vessel through said opening.
 8. A reactor vessel handlingmethod according to any one of claims 1 to 7, wherein said reactorvessel is carried out together with core internals.
 9. A reactor vesselhandling method according to any one of claims 1 to 8, wherein saidreactor vessel is carried out in a state in which a radiation shield iscombined with said reactor vessel.
 10. A reactor vessel handling methodcomprising the steps of, in a state in which an overhead traveling cranein a reactor containment vessel of a pressurized water reactor isremoved, carrying in a new reactor vessel to a predetermined positionwithin said reactor containment vessel through an opening provided in atop portion of said reactor containment vessel.
 11. A reactor vesselhandling method according to claim 10, wherein after carrying in saidnew reactor vessel, said overhead traveling crane is restored to anoriginal state.
 12. A reactor vessel handling method comprising thesteps of, in a state in which an overhead traveling crane in a reactorcontainment vessel of a pressurized water reactor is reinforced,carrying in a new reactor vessel to a predetermined position within saidreactor containment vessel through an opening provided in a side wall ofsaid reactor containment vessel.
 13. A reactor vessel handling methodaccording to claim 12, wherein reinforcing members for said overheadtraveling crane are removed after carrying in said new reactor vessel.14. A reactor containment vessel of a pressurized water reactor, whichcovers a reactor vessel and an overhead traveling crane installed abovesaid reactor vessel, wherein an opening allowing said reactor vessel tobe carried out through said opening is provided in at least one of a topwall and a side wall of said reactor containment vessel.
 15. A reactorcontainment vessel according to claim 14, wherein an opening/closingmechanism for opening and closing said opening is provided.